Abstract
Purpose: :
Precise alignment and orientation of fibers is essential to form a functional lens. We recently showed that Wnt-Frizzled/Planar Cell Polarity signaling regulates such coordinated behavior of lens fibers. We also found that each fiber has an apically situated primary cilium and this is polarized to the side of the cell facing the anterior pole. Since primary cilia can act as a sensor for extracellular guidance signals, we propose that in lens fibers the cilia detect a global guidance cue from the anterior pole and this coordinates their precise alignment/orientation. As part of a study to determine the function of primary cilia in lens we investigated the role of a key component of the intraflagellar transport (IFT) complex, IFT88, in cilia assembly in lens cells.
Methods: :
To detect expression of IFT88 we carried out immunofluorescent staining on paraffin sections of mouse lens using a specific IFT88 antibody. We also generated mice conditionally deficient for IFT88 in the lens using the established MLR10 transgenic Cre-line. Ciliogenesis in lenses of these mice was assessed by detecting the cilia marker, acetylated-tubulin, in histological sections and explants.
Results: :
We found IFT88 is expressed in lens epithelial and fiber cells. In both forms of lens cells, IFT88 co-localizes with the cilium axoneme marker, acetylated-tubulin. In mice conditionally deficient for IFT88, the protein was absent from most lens cells, although a few scattered cells did show some reactivity. In lens explants prepared from the IFT88 conditional knockout mice, the ciliary axoneme was reduced or absent.
Conclusions: :
These results indicate that IFT88 is essential for cilia assembly in lens cells. The ability to generate mice conditionally deficient for this key component of the IFT complex will provide an important tool to examine the role of primary cilia during lens development.
Keywords: development • signal transduction • cataract